Bark Bark @ other dogs.
 

My yorkie is 4 well 5 months old in 3 days. Every time she sees a dog, or hears one bark she get startled and starts barking and trying to find a way to get to the dog. When we go to parks it's a nightmare, every dog she sees, she immediately is determined to go after it. If she wasn't on a leash she would probably run to the dog and god knows what the other dog would do. She gets like this around my relatives pets as well, but as soon as she smells, greets the other pet she seems fine. But as soon as she sees the dog either stand up or walk away she barks and walks after it, it seems as if she wants to go wherever the other dog goes. This is my first yorkie puppy, i babysat older dogs (yorkie-poo mix) but never a yorkie. She doesn't seem to be aggressive and wanting to start up a fight with them but she does seem to just want to be around them, i am afraid however that even though she shows no aggression towards dogs the dogs she's meeting might jump on her and bite my poor little 3.5 lb yorkie. She is also very attracted towards being with larger dogs, hence my fear of them jumping on her.
I was just wondering what is it that i could do to help her stay calm around other dogs. She barks and barks and barks and to be honest i get a headache every now and then. I don't know whether this is a puppy thing she will grow out of or if it's something i should start really worrying about. The vet techs did tell me that it's a "puppy" thing and she'll grow out of it. and i truly hope it is but until then, how do i cope with it?

Your dog is seeing the other dog as a threat. Or she is trying to protect you.
My 7 year old still does this. I try to go at night so there aren't any dogs around. I haven't done anything to try to fix it but i think it is something they can grow out of if they are taught the right way.
I probably won't be of much help but i've been able to get my dog to bark less but stopping her while we are walking, crouch down and tell her a firm NO and hold her mouth shut (as best i can) to signal no barking. Let the dog pass and keep going. Once in a while the other dog walker will bring their dog over to greet, it's almost like they are curious and once they know, they won't bark. But my dog sometimes still freaks out when the other dog comes close. Who knows!